by Dan Vergano, USA TODAY

by Dan Vergano, USA TODAY

Bird flu experts on Wednesday ended a voluntary halt on research into how to make the deadly H5N1 avian influenza capable of spreading to mammals, and perhaps rapidly to people.

The international moratorium began last year following uproar over two studies that looked at genes that might make the bird flu readily transmissible between ferrets, a mammal model for infection from person-to-person. But 40 experts from nine nations now say they're ending the moratorium, citing international research safeguards that are in place against the release of their flu bugs to the public.

The studies released last year stirred controversy over two fears: one, that the work could lead to the unintended release from labs of highly lethal bugs that would be readily transmissible to people; the other that bioterrorists might use the studies as their cookbook on how to create a pandemic flu.

"We believe the public health benefits of H5N1 research outweigh the risks," says signer Yoshihiro Kawaoka of the University of Wisconsin, Madison. In their letter announcing the end of the moratorium, published in the journals Science and Nature, he and the other experts cited benefits to monitoring possible natural outbreaks of the disease and in testing possible vaccines against such an outbreak. "There can never be zero risk in research but we think the risk can be successfully managed," Kawaoka said in a briefing on the announcement.

Normally transmitted only from poultry to people, the H5N1 virus has killed some 360 people since 2003, largely farm workers in Asia and Egypt, according to the World Health Organization. Because the disease has a roughly 60% death rate based on WHO case numbers (although the true death rate is disputed), research has looked at how gene mutations might facilitate the spread of the disease from person to person in order to aid monitoring against such outbreaks happening naturally and to test possible vaccines against the bug.

In 2011, the two journals releasing the statement on Wednesday reported that a federal "biosafety" board had called for limiting information released in two bird flu transmission studies, one headed by Kawaoka and another by Ron Fouchier of Ersamus Medical Center in The Netherlands.

Originally only for 60 days, the moratorium on the research was intended to allow research funders and public health authorities to create safeguards against such concerns.

"We have done as much as we can as far as addressing the concerns," says National Institute of Allergy and Infectious Diseases chief Anthony Fauci. He says a framework for evaluating the safety of proposed H5N1 transmissibility research in mammals, up for public comment this month, should allow the research to resume receiving federal funding within weeks. "These decisions will always be made on a case-by-case basis with public health a chief concern," Fauci says. Research agencies in Europe and Asia have already put in place similar frameworks, which would add layers of safety review to research grant requests related to making bird flu more transmissible in the lab.

The research had led to sharply divided views among experts concerned with bioterrorism and lab safety, such as Michael Osterholm of the University of Minnesota, and other researchers who called the work fundamental to heading off a natural bird flu pandemic. "The lifting of the embargo on H5N1 transmission research is an important move forward for understanding what regulates influenza transmission," say virologist Vincent Racaniello of Columbia University. "In my view the moratorium has accomplished little other than delaying the conduct of important virology research."

In Europe, the research should begin again within weeks, Fourchier says. It will be aimed at determining the minimum number of genes needed to mutate to make the virus transmissible. First, he says, "we'll have to order more ferrets."